In a damper with variable damping force which has been proposed (for example, in Patent document 1), a valve element which is arranged in a flow channel between a reservoir and a cylinder containing a piston is opened or closed by an electromagnetic solenoid actuator so as to change the damping force of the damper. In addition, in another damper with variable damping force which has been proposed (for example, in Patent document 2), a valve element which is arranged in a flow channel formed in a piston contained in a cylinder is opened or closed by electromagnetic attractive force generated by an electromagnetic solenoid so as to change the damping force of the damper.